Call number: LD2668 .T4 1985 T36 / Master of Science

This thesis describes the experimental realisation and characterisation of three non-trivial trapping geometries for ultracold atoms. The double-well, ring and to some degree shell trap are examples of a highly versatile class of traps called time-averaged adiabatic potentials (TAAPs). In this experiment the TAAPs arise from the combination of three independent magnetic fields; a static quadrupole field dressed by a uniform radio-frequency field is time-averaged by a bias field oscillating at in the kHz regime. The result is a very smooth potential, within which ultracold atoms can be evaporatively cooled to quantum degeneracy, and subsequently manipulated into new geometries without destroying the quantum coherence. The vertically offset double-well potential provided the first example of ultracold atoms confined in a TAAP. The same potential is used to demonstrate efficient evaporative cooling across the Bose-Einstein condensate (BEC) phase transition using only the Landau-Zener loss mechanism. Switching off the time-averaging fields loads atoms from the double-well TAAP into the rf-dressed shell trap. A characterisation of this potential measured low heating rates and lifetimes of up to 58s. With efforts ongoing to increase the trap anisotropy, this potential shows promise for research into the static and rapidly rotating 2D systems. In the presence of a single time-averaging field, the shell geometry is transformed into a ring-shaped trap with an adjustable radius. The ring trap can be controllably tilted and progress towards multiply connected condensates is being made. A rotation scheme to spin up atoms in the ring trap has been demonstrated, presenting the opportunity to investigate the dynamics of superflow in degenerate quantum gases.

Baseado em uma seqüência já conhecida de Multislice Spin Echo convencional, implementamos uma seqüência do tipo Modified Driven Equilibrium Fourier Transform (MDEFT) adiabática multislice em um sistema de 2T e um de microimagens (9.4T). Essa metodologia utiliza, como pulso de inversão, um pulso de RF com modulação em amplitude e freqüência, conhecido por pulso adiabático. Dessa forma, os tempos de inversão são iguais para todos os planos selecionados, resultando num contraste por T1 uniformemente distribuído ao longo dos mesmos. O uso de um único e longo pulso adiabático de inversão tem, ainda, a vantagem de utilizar uma potência de pico menor para operar da mesma forma que um grupo de m pulsos convencionais. Utilizamos pulsos cujas modulações correspondentes de fase e freqüência foram calculadas com base nas condições de “Offset Independent Adiabaticity" (OIA) e a real eficiência dos mesmos foi avaliada através de simulações e experimentalmente. Para realização dos testes da metodologia desenvolvemos e caracterizamos dois “phantoms", cujas imagens demonstram a aplicabilidade da metodologia nos dois sistemas utilizados. / Based on the conventional Multislice Spin Echo pulse sequence, we implemented an adiabatic multislice Modified Driven Equilibrium Fourier Transform (MDEFT) pulse sequence on a 2T and a 9.4T microimaging system. This methodology uses, as inversion pulse, an amplitude and frequency modulated RF pulse, known as adiabatic pulse. In that way, the inversion times are the same for all slices, resulting in an evenly distributed T1 contrast. A single and long adiabatic inversion pulse has in addition the advantage of using a reduced peak power to perform in the same way as the group of m conventional pulses. We used pulses whose corresponding phase and frequency modulations were based on Offset Independent Adiabaticity and their real efficiency were evaluated both through simulations and experimentally. To test the methodology, we developed and characterized two phantoms, whose images demonstrate the applicability of the methodology in the two mentioned systems.

Ho, Tak Ngai = 中子星在絶熱冷卻下的不穩定性 : 數值模擬和簡單類比 / 何德藝. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 101-102). / Abstracts in English and Chinese. / Ho, Tak Ngai = Zhong zi xing zai jue re leng que xia de bu wen ding xing : shu zhi mo ni he jian dan lei bi / He Deyi. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- The astrophysical problem --- p.2 / Chapter 2.1 --- Neutron stars --- p.2 / Chapter 2.2 --- Equations --- p.4 / Chapter 2.3 --- EOS --- p.6 / Chapter 2.4 --- Equilibrium configurations --- p.8 / Chapter 2.5 --- Stability --- p.9 / Chapter 2.6 --- The key equilibrium properties --- p.10 / Chapter 2.7 --- Adiabatic cooling --- p.11 / Chapter 2.8 --- Modeling adiabatic cooling by varying T --- p.13 / Chapter 3 --- Numerical Simulations in GR --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.2 --- The equations and the EOS --- p.17 / Chapter 3.3 --- Evolution of a stellar system in GR --- p.20 / Chapter 3.4 --- Results --- p.22 / Chapter 4 --- Newtonian model --- p.27 / Chapter 4.1 --- Introduction --- p.27 / Chapter 4.2 --- Newtonian fluid equations --- p.28 / Chapter 4.3 --- Polytropes --- p.28 / Chapter 4.4 --- Model EOS --- p.31 / Chapter 4.5 --- Equilibrium solutions --- p.33 / Chapter 4.6 --- Stability --- p.35 / Chapter 4.7 --- Dynamics --- p.38 / Chapter 4.8 --- Adiabatic changes --- p.42 / Chapter 4.9 --- Results --- p.46 / Chapter 5 --- Model of instability --- p.52 / Chapter 5.1 --- Introduction . --- p.52 / Chapter 5.2 --- Analytical study of the model --- p.54 / Chapter 5.3 --- Numerical verification --- p.55 / Chapter 5.4 --- Summary --- p.59 / Chapter 6 --- Model of criticality --- p.62 / Chapter 6.1 --- Introduction --- p.62 / Chapter 6.2 --- General discussion of equilibrium properties --- p.63 / Chapter 6.3 --- Construction of model --- p.67 / Chapter 6.4 --- Study of the model --- p.75 / Chapter 6.5 --- Conclusion --- p.82 / Chapter 7 --- Conclusion --- p.85 / Appendix --- p.87 / Chapter A --- Neutron stars cooling due to neutrinos emission --- p.87 / Chapter B --- Determining how r change --- p.89 / Chapter C --- Basic equations in the GR context --- p.91 / Chapter C.1 --- ADM formulation of the field equations --- p.91 / Chapter C.2 --- Explicit form of the hyperbolic equation --- p.93 / Chapter D --- One-zone model --- p.95 / Chapter E --- Numerical scheme of getting the EOS --- p.98 / Bibliography --- p.101

CMOS based computing is reaching its limits. To take computation beyond Moores law (the number of transistors and hence processing power on a chip doubles every 18 months to 3 years) requires research explorations in (i) new materials, devices, and processes, (ii) new architectures and algorithms, (iii) new paradigm of logic bit representation. The focus is on fundamental new ways to compute under the umbrella of rebooting computing such as spintronics, quantum computing, adiabatic and reversible computing. Therefore, this thesis highlights explicitly Quantum computing and Adiabatic logic, two new computing paradigms that come under the umbrella of rebooting computing. Quantum computing is investigated for its promising application in high-performance computing. The first contribution of this thesis is the design of two resource-efficient designs for quantum integer division. The first design is based on non-restoring division algorithm and the second one is based on restoring division algorithm. Both the designs are compared and shown to be superior to the existing work in terms of T-count and T-depth. The proliferation of IoT devices which work on low-power also has drawn interests to the rebooting computing. Hence, the second contribution of this thesis is proving that Adiabatic Logic is a promising candidate for implementation in IoT devices. The adiabatic logic family called Symmetric Pass Gate Adiabatic Logic (SPGAL) is implemented in PRESENT-80 lightweight algorithm. Adiabatic Logic is extended to emerging transistor devices.

Ethylene oxide (EO) is a very versatile compound with considerable energy in its ring structure. Its reactions proceed mainly via ring opening and are highly exothermic. Under some conditions, it is known to undergo a variety of reactions, such as isomerization, polymerization, hydrolysis, combustion and decomposition Due to its very reactive characteristic and widely industrial applications, EO has been involved in a number of serious incidents such as Doe Run 1962, Freeport 1974, Deer Park 1988 and Union Carbide Corporation’s Seadrift 1991. The impacts can be severe in terms of death and injury to people, damage to physical property and effects on the environment. For instance, the Union Carbide incident in 1991 caused one fatality and extensive damage to the plant with the property damage of up to 80 million dollars. Contamination has a considerable impact on EO reactivity by accelerating substantially its decomposition and playing a key role on EO incidents. In this work, the reactivity of EO with contaminants such as KOH, NaOH, NH4OH, and EDTA is evaluated. Useful information that is critical to the design and operation of safer chemical plant processes was generated such as safe storage temperatures (onset temperature), maximum temperature, maximum pressure, temperature vs. time, heat and pressure generation rates as a function of temperature and time to maximum rate using adiabatic calorimetry. A special arrangement for the filling-up of the cell was constructed due to the gaseous nature and toxicity of EO. A comparison of their thermal behavior is also presented since several contaminants are studied.

The focus of this dissertation is the study of the photodissociation dynamics of halogen oxide species (XO, X = Cl, Br, I). These radical species are known to be important in stratospheric and tropospheric ozone depletion cycles. They are also useful benchmark systems for the comparison to current theoretical methods where they provide insight into the dynamics occurring beyond the Franck-Condon region. These systems are studied using velocity map ion imaging, a technique that measures velocity and angular information simultaneously. Photofragment species are state-selectively ionized for detection using 2+1 REMPI (Resonance Enhanced Multi-Photon Ionization). The instrumentation employs a molecular beam of the XO radicals formed using pyrolitic and photolytic methods. The current work involves the measurement of fundamental physical constants of the XO species. The bond dissociation energy of IO is measured. Vibrational level dependent correlated final state branching ratios of the predissociation of the A(^2 II_3/2) state of ClO and BrO are reported, and comparison to theoretical methods is discussed.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 157-163). Available also in a digital version from Dissertation Abstracts.

As the hydrodynamic theory breaks down with the local density ap- proximation in the fermionic superfluid with spin-polarization, we develop a general formalism of the adiabatic dynamics for the low-lying collective modes in the BEC-BCS crossover, which is exact in the adiabatic limit. This adi- abatic dynamic theory is based on a static density functional theory of the spin-polarized superfluid system, which we derive as a generalization of the conventional density functional theory of superfluid for current experimental interests. A special case where the system is uniform and analytically solv- able is studied in detail. We show that our adiabatic equations of motion are reduced to the hydrodynamic equations of motion within local density approx- imation, which provides a solid microscopic foundation for the well-publicized phenomenological hydrodynamic theory. / text

Στην παρούσα εργασία μελετάμε την κυκλική μεταφορά πληθυσμών σε κβαντικά συστήματα με σπασμένη συμμετρία μέσω εξαναγκασμένης αδιαβατικής μετάβασης Raman (STIRAP) στην οποία προσθέτουμε μια διαδικασία ενός φωτονίου που κλείνει τον κύκλο μετάβασης. Αρχικά μελετάμε το σύστημα θεωρητικά για καθαρούς παλμούς ενώ στη συνέχεια προσθέτουμε όρους θορύβου και αποσβεσης (decay) προσεγγίζοντας, έτσι, περισσότερο ένα ρεαλιστικό σύστημα. Η μελέτη του δεύτερου μέρους βασίζεται στη λύση των εξισώσεων του συστήματος με αριθμητικές μεθόδους. / We study cyclic population transfer in quantum systems with broken symmetry through stimulated Raman adiabatic passage (STIRAP) in which we add a one-photon process that closes the STIRAP two-photon process. After the initial theoretical treatment of the problem, for simple Gaussian pulses, we later add noise and decay terms in the Hamiltonian of the system, rendering a more realistic approach. On the second part of this study we use numerical methods to solve the equations found.